Solubility of chemical warfare agent simulants in supercritical carbon dioxide: experiments and modeling

Abstract

Solubility data are reported for ethyl phenyl sulfide (EPS) and 2-chloroethyl ethyl sulfide (CEES) in CO 2 at temperatures from 25 to 100 °C. These two sulfide-based compounds are homomorphs for chemical warfare agents (CWAs). Both sulfide–CO 2 mixtures exhibit type-I phase behavior. The maximum in the 100 °C isotherm is approximately 2600 psia for the CEES–CO 2 system and approximately 3400 psia for the EPS–CO 2 system. The Peng–Robinson equation of state (PREOS) is used to model both sulfide–CO 2 mixtures as well as the phase behavior of the 2-chloroethyl methyl sulfide (CEMS)–CO 2 system previously reported in the literature. The Joback–Lydersen group contribution method is used to estimate the critical temperature, critical pressure, and acentric factor for the sulfides. Semi-quantitative estimates of the phase behavior are obtained for the CEES–CO 2 and EPS–CO 2 systems with a constant value of k ij , the binary interaction parameter, fit to the 75 °C isotherms. However, very poor fits are obtained for the 2-chloroethyl methyl sulfide–CO 2 system regardless of the value of k ij . On the basis of the high solubility of EPS and CEES in CO 2, supercritical fluid (SCF)-based technology could be used to recycle or recover chemical warfare materials.